Saul Perlmutter is an American astrophysicist at the Lawrence Berkeley National Laboratory and a Professor of Physics at the University of California, Berkeley.

He is a member of the American Academy of Arts & Sciences, and was elected a Fellow of the American Association for the Advancement of Science. He is also a member of the National Academy of Sciences. Perlmutter shared both the 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics with Brian P. Schmidt and Adam Riess for providing evidence that the expansion of the universe is accelerating.

He graduated with an AB in physics from Harvard magna cum laude in and received his PhD in physics from the University of California, Berkeley. Perlmutter's PhD thesis titled "An Astrometric Search for a Stellar Companion to the Sun" described the development and use of an automated telescope to search for Nemesis candidates under Richard A. Muller. At the same time, he was using this telescope to search for Nemesis and supernova, which would lead him to his award winning work in cosmology.

Perlmutter heads the Supernova Cosmology Project at Lawrence Berkeley National Laboratory, where his findings initiated new lines of research to understand the nature of the universe, including the exploration of dark matter. For this work Perlmutter was awarded the 2011 Nobel Prize in Physics, shared jointly with Riess and Schmidt.

Perlmutter is also a lead investigator in the Supernova/Acceleration Probe project, which aims to build a satellite dedicated to finding and studying more supernovae in the distant universe. This will help to better constrain the rate at which the universe is accelerating. He is also a participant in the Berkeley Earth Surface Temperature project, which aims to increase our understanding of recent global warming through improved analyses of climate data.